Insoluble polymers which can swell only slightly with modified amino groups, processes for their preparation, and their use

ABSTRACT

An insoluble, only slight swellable, polymer having modified amino groups, which contain units of the formulae: ##STR1## or both (I) and (II), wherein R 1 , R 2 , R 3  and Me are as defined herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to insoluble, only slightly swellablepolymers having modified amino groups, processes for the preparation ofsuch polymers and the use of the insoluble, only slightly swellablepolymers having modified amino groups as adsorber resin for metal ionsand ion exchangers.

2. Description of the Background

DE-A-23 03 081 discloses the preparation of water-soluble reactionproducts of polyethyleneimine with the sodium salt of chloroacetic acidin aqueous solution. Water-soluble polyethyleneimines havingiminodiacetic acid groups are obtained. The water-soluble polymers areused as complexing agents for metal ions.

U.S. Pat. No. 3,424,790 discloses the preparation of water-soluble,carboxymethylated polyethyleneimines by a multistage process. First,equivalent amounts of polyethyleneimine are reacted with formaldehyde atfrom -15 to 40° C. Thereafter, the adduct is reacted with hydrogencyanide or alkali metal cyanides, likewise at from -15 to 40° C., andthe reaction products are hydrolyzed with alkali metal hydroxides atfrom 50 to 110° C. in a subsequent reaction stage. EP-B-071 050discloses partially hydrolyzed polymers of N-vinylformamide whichcontains from 90 to 10 mol % of vinylamine units and from 10 to 90 mol %of N-vinylformamide units. EP-A-0 216 387 describes copolymers ofN-vinylformamide with other ethylenically unsaturated monomers. Thepolymerized N-vinylformamide units can be converted into vinylamineunits by hydrolysis with acids or bases. Polymers containing vinylamineunits are furthermore described in EP-A-0 262 577, EP-A-264 649 andEP-A-0 251 182.

WO-A-94/11408 discloses insoluble, only slightly swellable polymerswhich contain polymerized vinylamine units. These polymers are preparedby polymerizing N-vinylcarboxamides and, if required, othermonoethylenically unsaturated monomers copolymerizable with saidN-vinylcarboxamides with, as crosslinking agents, compounds containingat least two ethylenically unsaturated double bonds, in the absence ofoxygen and polymerization initiators, to give popcorn polymers, and thenhydrolyzing the polymerized N-vinylcarboxamide units to give vinylamineunits by the action of acids, bases or enzymes. The amino-containingpopcorn polymers are used as ion exchangers or as adsorber resin formetal ions. The polymers described above and containing N-vinylglycineor N-vinyliminodiacetic acid units are water-soluble. If they are usedas complexing agents for metal ions dissolved in water, expensivetechnology is required for separating the polymeric complexes from thesolution.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide novel substances.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

We have found that this object is achieved, according to the invention,by insoluble, only slightly swellable polymers which have modified aminogroups and contain units of the formulae ##STR2## where R¹ is H, C₁ -C₆-alkyl

R²,R³ are each H, C₁ -C₂₀ -alkyl, aryl, aralkyl

Me is H, or one equivalent of an alkali metal, of an alkaline earthmetal or of ammonium.

The present invention furthermore relates to a process for the 35preparation of insoluble, only slightly swellable polymers havingmodified amino groups. In the process, an insoluble, only slightlyswellable polymer which contains units of the formula ##STR3## where R¹is H or C₁ -C₆ -alkyl, is reacted with (1) α-halocarboxylic acids oralkali metal, alkaline earth metal or ammonium salts thereof

or

(2) aldehydes and hydrogen cyanide or an alkali metal cyanide or

cyanohydrins obtained from aldehydes and alkali metal cyanide, andcarrying out hydrolysis of the adducts.

The present invention furthermore relates to the use of the insoluble,only slightly swellable polymers having modified amino groups asadsorber resins for metal ions and as ion exchangers.

The novel polymers are obtained by a multistage process. First, popcornpolymers which are insoluble in all solvents and only slightly swellabletherein are prepared by known methods. For this purpose, monomers whichbelong to the abovementioned groups (a), (b) and (c) are polymerized.

Monomers of group (a) which are used for the preparation of the knownpopcorn polymers are N-vinylcarboxamides of the formula ##STR4## where Rand R¹ are each H or C₁ -C₆ -alkyl.

Suitable compounds of the formula IV are, for example,N-vinyl-formamide, N-vinyl-N-methylformamide, N-vinylacetamide,N-vinyl-N-methylacetamide, N-vinyl-N-ethylformamide,N-vinyl-N-n-propyl-formamide, N-vinyl-N-isopropylformamide,N-vinyl-N-isobutylformamide, N-vinyl-N-methylpropionamide,N-vinyl-n-butylacetamide and N-vinyl-N-methylpropionamide. From thisgroup of monomers, N-vinylformamide is preferably used.

Monomers of group (b), which may be present in the preparation ofpopcorn polymers are other monoethylenically unsaturated monomerscopolymerizable with the monomers of groups (a) and (c). These include,for example, acrylamide, methacrylamide, acrylic acid, methacrylic acid,acrylates, methacrylates and/or vinyl esters. The acrylates andmethacrylates are preferably derived from saturated, monohydric alcoholsof 1 to 4 carbon atoms or saturated dihydric alcohols of 2 to 4 carbonatoms. Examples of these esters are methyl acrylate, methylmethacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate,n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate andthe esters of acrylic acid and methacrylic acid which are derived fromthe isomeric butanols, as well as hydroxyethyl acrylate, hydroxyethylmethacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate,hydroxybutyl acrylate, hydroxyisobutyl acrylate and hydroxyisobutylmethacrylate. Preferred vinyl esters are vinyl formate, vinyl acetateand vinyl propionate. Other suitable monomers of group (b) areacrylonitrile, methacrylonitrile, N-vinylpyrrolidone,N-vinylcaprolactam, 1-vinylimidazole, 2-methyl-1-vinylimidazole and4-methyl-1-vinylimidazole. The monomers of group (b), alone or as amixture with one another, can be polymerized together with the monomersof groups (a) and (c). Among the monomers of group (b),N-vinylpyrrolidone is particularly suitable for the preparation ofpopcorn polymers.

Where they are used in the preparation of the popcorn polymers, themonomers of group (b) are present in an amount of from 0.1 to 80% byweight in the monomer mixture comprising (a) and (b).

Compounds which act as crosslinking agents and contain at least twoethylenically unsaturated nonconjugated double bonds in the molecule areused as monomers of group (c) in the polymerization. For example,alkylenebisacrylamides, such as methylenebisacrylamide, andN,N'-acryloylethylenediamine, N,N'-divinylethyleneurea,N,N'-divinylpropyleneurea, ethylidene-bis-3-(N-vinylpyrrolidone),N,N'-divinyl-2,2'-diimidazolylbutane and1,1'-bis(3,3'-vinyl-benzimidazolin-2-one)-1,4-butane are particularlysuitable. Other suitable crosslinking agents are, for example, alkyleneglycol di(meth)acrylates, such as ethylene glycol diacrylate, ethyleneglycol dimethacrylate, tetraethylene glycol acrylate, tetraethyleneglycol dimethacrylate, diethylene glycol diacrylate, and diethyleneglycol dimethacrylate, aromatic divinyl compounds, such asdivinylbenzene and divinyltoluene, and vinyl acrylate, allyl acrylate,allyl methacrylate, divinyldioxane, penta-erythrityl triallyl ether andmixtures of the crosslinking agents. The crosslinking agents are used inamounts of from 0.1 to 10, preferably 1 to 4, % by weight, based on themonomers (a) and (b) used in the polymerization.

The popcorn polymerization is carried out by known processes, forexample as precipitation polymerization or by mass polymerization. Aprocedure in which, as described in EP-B-0 177 812, the popcornpolymerization is initiated by heating a mixture of from 99.6 to 98.8%by weight of N-vinylpyrrolidone and 0.4 to 1.2% by weight of a compoundhaving at least two ethylenically unsaturated double bonds, ascrosslinking agent, to 100 to 150° C. in the absence of oxygen andpolymerization initiators is preferred. This polymerization is initiatedin particular by the presence of small amounts of sodium hydroxidesolution or potassium hydroxide solution. A polymerizable popcornpolymer forms within a short time and, with addition of other suitablemonomer mixtures, i.e. the monomers of group (a) and, if required, (b)and further addition of monomers (c), initiates the popcornpolymerization of these monomers without an induction period.

In order to carry out the popcorn polymerization without solvents, themonomer mixture of (a) and (c) and, if required, (b) is rendered inertby passing in nitrogen and is then heated to 100-200° C., preferably150-180° C. It is advantageous to continue passing a gentle stream ofnitrogen through the monomers even during the polymerization. Exclusionof oxygen is also achieved by polymerizing the batch at a pressure whichis below atmospheric pressure and at which the monomers boil. Thepulverulent popcorn polymers have an average particle size of from about10 μm to 5 mm, preferably from 10 μm to 500 μm.

Precipitation polymerization in water at monomer concentrations of from5 to 30% by weight, at from 20 to 200° C. and a pH above 6 is preferredfor the preparation of the popcorn polymers. Further information on thepreparation of the popcorn polymers and hydrolysis of the polymerizedN-vinylcarboxamide units is given in WO-A-94/11408. The popcorn polymerscontain, for example, from 20 to 100% by weight of N-vinylcarboxamidesof the formula IV as polymerized units.

In the hydrolysis, at least 0.5% of the polymerized N-vinylcarboxamidesof the formula IV are hydrolyzed with formation of amino groups. Thehydrolysis is continued until at least the 0.1%, preferably at least20%, of the N-vinylcarboxamide units present in the popcorn polymershave been hydrolyzed. The examples of suitable hydrolysis agents areacids, bases and enzymes.

Suitable acids are, for example, mineral acids, such as hydrogen halide(gaseous or aqueous solution), sulfuric acid, nitric acid or phosphoricacid (ortho-, meta- or polyphosphoric acid) or organic acids, forexample C₁ -C₅ -carboxylic acids, such as formic acid, acetic acid orpropionic acid, or aliphatic and aromatic sulfonic acids, such asmethanesulfonic acid, benzenesulfonic acid or toluenesulfonic acid. Inthe hydrolysis with acids, the pH is 0 to 5. From 0.05 to 1.5,preferably from 0.4 to 1.2, equivalents of acid are required percarboxyl radical to be eliminated in the polymer.

After acidic hydrolysis, the popcorn polymers containing amino functionsare present as a rule as salts, suitable opposite ions being thecorresponding acid anions or anions of the liberated carboxylic acids,for example formate. For the preparation of the novel water-insolublepolymers, it is advantageous partially or completely to deprotonate thepolymers in aqueous suspension by adding bases. Particularly suitablebases are alkali metal and alkaline earth metal hydroxides, inparticular sodium hydroxide, alkali metal and alkaline earth metalcarbonates, in particular sodium carbonate, ammonia and alkylderivatives of ammonia. The salts formed in the neutralization, e.g.sodium sulfate, remain in aqueous solution.

In the hydrolysis with bases, hydroxides of metals of the first andsecond main groups of the Periodic Table may be used, for examplelithium hydroxide, sodium hydroxide, potassium hydroxide, calciumhydroxide, strontium hydroxide and barium hydroxide. However, ammonia oralkyl and aryl derivatives of ammonia, for example alkylamines orarylamines, such as triethylamine, mono-ethanolamine, diethanolamine,triethanolamine, morpholine, piperidine, pyrrolidine or aniline, arealso suitable. In the hydrolysis with bases, the pH of the reactionmixture is, for example, from 8 to 14. The bases can be used in thesolid, liquid, or, if required, also gaseous state, diluted orundiluted. Ammonia, sodium hydroxide solution or potassium hydroxidesolution is preferably used. The hydrolysis in the acidic or alkaline pHrange is carried out at from 20 to 170° C., preferably from 50 to 120°C. It is complete after from about 2 to 8, preferably from 3 to 5 hours.A procedure in which the acids or bases are added in aqueous solutionhas proven particularly useful. After the hydrolysis, neutralization isgenerally carried out, so that the pH of the hydrolyzed polymer solutionis from 2 to 8, preferably from 3 to 7. The neutralization is requiredwhen it is intended to prevent or delay the continuation of thehydrolysis of partially hydrolyzed polymers. For the further processing,the hydrolysis with the aid of bases has the advantage that anadditional neutralization step is superfluous.

The hydrolysis may also be carried out with the aid of enzymes, forexample proteases, ureases or amidases.

The water-insoluble popcorn polymers which contain vinylamine units andare only slightly swellable may be isolated from the aqueous suspension.However, it is also possible to carry out the subsequent reaction withα-halocarboxylic acids or hydrogen cyanide or alkali metal cyanides andaldehydes immediately after the hydrolysis.

The novel reaction of the insoluble polymer containing vinylamine unitswith α-halocarboxylic acids takes place unexpectedly smoothly andquantitatively. Owing to its insolubility in solvents, a chemically andphysically crosslinked polymer should furthermore be attacked byreagents only with very great difficulty, if at all. However, dependingon the reaction conditions, i.e. the amount of α-halocarboxylic acidused or the salts thereof and the reaction medium, reaction time and thereaction temperature, popcorn polymers having modified amino groups ofthe formulae I and II, ##STR5## where R¹ is H or C₁ -C₆ -alkyl, R² andR³ are each H, C₁ -C₂₀ -alkyl, aryl, or aralkyl and Me is H or oneequivalent of an alkali metal, of an alkaline earth metal or ofammonium, are in fact obtained. Both structure I and structure II may beformed from primary vinylamine units (R¹ ═H). In the case of secondaryvinylamine units (R¹ ≠H) only structure I is possible. Popcorn polymershaving primary vinylamine units (R¹ ═H) are preferably used as startingmaterials.

Suitable α-halocarboxylic acids are all compounds of the formula##STR6## where R², R³ are each H, C₁ -C₂₀ -alkyl, aryl or aralkyl and Meis H, or one equivalent of an alkali metal, of an alkaline earth metalor of ammonium and X is halogen, such as F, Cl, Br or I. Suitableα-halocarboxylic acids of the formula V are, for example, chloroaceticacid, bromoacetic acid, iodoacetic acid, α-chloropropionic acid,α-bromopropionic acid, α-iodopropionic acid, α-chlorobutyric acid,α-bromobutyric acid, α-chlorisobutyric acid, α-bromocaproic acid,2-chlorovaleric acid, 2-bromophenyl acetic acid,2-chloro-3-phenylpropionic acid, 2-bromo-3-phenylpropionic acid,α-chlorolauric acid and α-bromopalmitic acid. Chloroacetic acid ispreferably used.

The α-halocarboxylic acids may be used as such or in the form of theirsalts. Suitable opposite ions are monovalent or polyvalent metal ions,for example alkali metal or alkaline earth metal ions. Ammonium ions oralkyl derivatives thereof, for example methyl-, dimethyl-, trimethyl- ortetramethylammonium ions or other alkylammonium ions, are also suitable.Sodium salts are preferably used as starting materials.

Usually, from 0.05 to 5.0, preferably from 0.1 to 2.2, equivalents ofα-halocarboxylic acid or alkali metal or alkaline earth metal saltthereof are required per amine unit in the popcorn polymer.

The reaction is carried out in suspension, preferably in a medium inwhich the α-halocarboxylic acid or its salt is soluble. Inert solvents,e.g. water, methanol, ethanol, isopropanol, ethylene glycol, diethyleneglycol, acetonitrile, acetone, tetrahydrofuran, dioxane,N-methylpyrrolidone, diethylether, cyclohexane, pentane, benzene ortoluene, and mixtures of the stated solvents are most suitable. Thereaction is preferably carried out in water, methanol, ethanol or amixture of these solvents. The polymer content of the suspension is, forexample, from 0.1 to 50, preferably from 1 to 20, % by weight, so thatthorough mixing is ensured during the reaction in order to avoidagglomeration. A procedure in which the α-halocarboxylic acid or one ofits salts is added in solution has proven particularly useful. When thereaction is carried out in an aqueous medium, a pH of from 7 to 12,preferably from 8 to 10 is established.

The reaction is carried out at from 20 to 180° C., preferably from 50 to150° C., very particularly preferably from 60 to 110° C. At temperaturesabove the boiling point of the reaction medium, the reaction is carriedout under pressure in an appropriate pressure-resistant container. Thereaction time is, for example, from 1 to 30, preferably from 6 to 20hours. The conversion can be determined, for example, by quantitativeanalysis of the halide liberated during the reaction.

A further possibility for modifying the amino groups in the popcornpolymers so that insoluble, only slightly swellable polymers havingunits of the formulae I and/or II are obtained comprises reactingpopcorn polymers containing polymerized vinylamine units with

aldehydes and hydrogen cyanide or alkali metal cyanides or

cyanohydrins obtained from aldehydes and alkali metal cyanide, andcarrying out subsequent hydrolysis of the adducts in each case.

Suitable aldehydes are, for example, formaldehyde, acetaldehyde,propionaldehyde, n-butyraldehyde, pentanal, hexanal, heptanal, octanal,decanal, benzaldehyde and oxo aldehydes, such as C₁₃ /C₁₅ oxo aldehydesor C₉ /C₁₁ oxo aldehydes. Mixtures of a plurality of aldehydes may alsobe used. Formaldehyde is preferably used, usually in the form of aconcentrated aqueous solution. Readily volatile aldehydes such asformaldehyde and acetaldehyde, can however also be passed in gaseousform into the reaction mixture.

Examples of suitable alkali metal cyanides are sodium cyanide andcalcium cyanide, sodium cyanide being preferably used. Ammonium cyanidemay also be used.

The reaction is carried out in a medium in which the aldehyde andcyanide dissolve to a sufficient extent, e.g. water, methanol, ethanol,isopropanol, n-propanol, n-butanol, ethylene glycol, diethylene glycol,acetonitrile, acetone, tetrahydrofuran, dioxane or N-methylpyrrolidone,or mixtures of the stated solvents. The reaction is preferably carriedout in water. The reaction with hydrogen cyanide is carried out, forexample, at a pH of from 0 to 10, preferably from 2 to 6. If, on theother hand, alkali metal cyanide is used, a pH of, for example, from 8to 14, preferably from 10 to 12, is advisable. The polymer content ofthe suspension is, for example, from 0.1 to 50, preferably from 1 to 20,% by weight, so that thorough mixing is ensured during the reaction toprevent agglomeration.

The aldehyde and hydrogen cyanide or alkali metal cyanide are preferablyused in equimolar amounts, so that 0.1 to 100% of the amino functionspresent in the polymer are carboxymethylated. Usually, from 0.15 to 3.0,preferably from 0.2 to 2, equivalents of aldehydes and alkali metalcyanides are required per NH₂ group. Excess amounts of aldehyde oralkali metal cyanide present no problems because they can be readilyseparated off from the reaction product. Popcorn polymers having unitsof the formula I or II and popcorn polymers which contain units of theformula I and II are obtained from popcorn polymers having primaryvinylamine units (R¹ ═H), whereas only the units of the formula I areformed in the case of popcorn polymers having secondary vinylamineunits. Popcorn polymers which are obtainable by polymerizingN-vinylformamide and have primary amino groups are preferably used asstarting materials.

Reaction may be carried out either continuously or batchwise. As a rule,aldehydes and hydrogen cyanide or alkali metal cyanide in aqueoussolutions are added to the polymer suspension at from -15 to 100° C.,preferably from 0 to 70° C., and said suspension is then stirred forsome time at from 20 to 180° C., preferably from 50 to 150° C., and veryparticularly preferably from 60 to 110° C., to complete the reaction.The reagents may be metered in either all at once or separately from oneanother over a period of, for example, 0.5 to 10 hours. The procedure inwhich the aldehyde and hydrogen cyanide or alkali metal cyanide aremetered in simultaneously in solution is particularly advantageous, theconcentration of cyanide in the reaction mixture being brought to 1 to50% above the concentration of aldehyde during the addition. This meansin practice that hydrogen cyanide or alkali metal cyanide is meteredinto the polymer at a slightly higher rate than the aldehyde or,alternatively, cyanide is metered in at the same rate but before thealdehyde. This suppresses the formation of by-products.

The reaction can be carried out at atmospheric, superatmospheric orreduced pressure. The reaction with alkali metal cyanides in the alkalipH range is preferably carried out under reduced pressure in order toremove from the reaction mixture the ammonia formed during thehydrolysis. In another preferred embodiment of the process, an inert gasstream, e.g. air or nitrogen, is passed through the reaction mixtureduring the reaction. A particularly preferred procedure is one whichentails simultaneous stripping with an inert gas and the use of reducedpressure, for example from 100 to 900, preferably from 500 to 800, mbar.If hydrogen cyanide is used, the initially obtained cyanoalkylatedproduct is subsequently hydrolyzed in a second step with the aid ofbases, preferably sodum hydroxide solution. The intermediate may beeither isolated or further processed in the same reaction medium. Thehydrolysis is preferably carried out under reduced pressure whilststripping with an inert gas. By repeating the carboxyalkylationreaction, it is possible to increase the degree of carboxyalkylation ofthe amino-containing popcorn polymers.

At the end of the reaction, the novel popcorn polymers can be isolated,for example, by filtration or centrifuging with subsequent washing outof the salts present with the corresponding suspending agent, preferablywith water or alcohol, and drying in a conventional dryer, such as athrough-circulation dryer or vacuum drying oven, a paddle dryer or apneumatic dryer. The polymers are insoluble in water and all knownsolvents and furthermore swell only slightly therein.

The insoluble, carboxyl-carrying popcorn polymers are suitable forremoving metal ions from solutions. The type of solvent is notimportant. However, the process is preferably applied to aqueoussolutions of metal ions, for example Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Al³⁺, Ga³⁺,Rb⁺, Cs⁺, Cu²⁺, Ag⁺, Au³⁺, Fe²⁺, Fe³⁺, Ni²⁺, Pd²⁺, Pt²⁺, Co²⁺, Rh²⁺,Ir²⁺, Cr³⁺, Mn²⁺, Mn³⁺, Zn²⁺, Cd²⁺, Hg²⁺, Sn²⁺ and Pb²⁺. The anions ofthe metal salts have scarcely any effect on the removability of themetal ions from the solutions. The amounts of popcorn polymer havingunits of formulae I and/or II are chosen so that the number of mols ofavailable carboxyl groups is at least equivalent to the number of metalions in the solution. A molar excess of carboxyl groups is preferablyused. For substantial complexing of the metal ions, from 2 to 100,preferably more than 50, mol % of the carboxyl functions of the popcornpolymers should be present in deprotonated form. In an advantageousprocedure, the novel popcorn polymer having an appropriate amount ofcarboxyl functions is added to a metal salt solution. However, it isalso possible to suspend such popcorn polymers as free acids in themetal salt solution and to increase the pH of the solution by addingbases, e.g. sodium hydroxide solution or ammonia, and thus todeprotonate the carboxyl functions. Marked complexing is observable inthe case of Cu²⁺ even at a pH above 5.

The complexing power of the carboxyl-carrying polymers is determined byquantitative analysis of the metal ions remaining in the solution.Suitable methods of analysis are, for example, complexometric titrationand atomic absorption spectroscopy or spectralphotometry.

EXAMPLES Example 1

Popcorn polymer 1

10 g of popcorn polymer having the molar composition of 87.7% ofvinylamine×1/2 H₂ SO₄ units, 4.6% of N-vinylformamide units, 6.6% ofN-vinylpyrrolidone units and 1.1% of N,N'-divinylethyleneurea units(≡118 mmol of protonated vinylamine functions) are suspended in 300 g ofwater in a stirred apparatus having a reflex condenser and thermometer.42.5 g of 97% strength sodium chloroacetate (≡354 mmol) are added and pHis brought to 10 with 49 g of 25% strength aqueous sodium hydroxidesolution. The suspension is then heated at 80° C. for 10 hours withthorough stirring. After cooling to room temperature, the solid isfiltered off with suction, washed several times with water and dried for24 hours at 100° C. and 100 mbar in a vacuum drying oven. 17.8 g ofcarboxymethylated popcorn polymer having 73.7 mol % of units of thestructure I (R¹, R², R³ ═H, Me═Na) and 14.0 mol % of the structure II(R², R³ ═H, Me═Na) are obtained.

Example 2

Popcorn polymer 2

10 g of a popcorn polymer having a molar composition of 73.4% ofvinylamine×1/2 H₂ SO₄ units, 8.1% of N-vinylformamide, 17.4% ofN-vinylpyrrolidone units and 1.1% of N,N'-divinylethyleneurea units (≡93mmol of protonated vinylamine functions) are reacted with 39 g of 97%strength sodium chloroacetate (≡325 mmol) and 45 g of 25% strengthaqueous sodium hydroxide solution, as described in Example 1. 16.5 g ofcarboxymethylated popcorn polymer having 78.0 mol % of units of theformula I (R¹, R², R³ ═H, Me═Na) and 22.0 mol % of units of the formulaII where R² and R³ are H and Me is Na are obtained.

Example 3

Popcorn polymer 3

10 g of a popcorn polymer having a molar composition of 56.0% ofvinylamine×1/2 H₂ SO₄ units, 4.2% of vinylformamide, 38.5% ofN-vinylpyrrolidone units and 1.3% of N,N'-divinylethyleneurea units(≡64.1 mmol of protonated vinylamine functions) are reacted with 30.8 gof 97% strength sodium chloroacetate (≡256.4 mmol) and 24 g of 25%strength aqueous sodium hydroxide solution as described in Example 1.14.4 g of carboxymethylated popcorn polymer having 44.8 mol % of unitsof the formula I where R¹, R², R³ are H and Me is Na and 11.2 mol % ofunits of the formula II where R² and R³ are H and Me is Na are obtained.

Example 4

Popcorn polymer 4

10 g of a popcorn polymer having a molar composition of 29.7% ofvinylamine×1/2 H₂ SO₄ units, 4.1% of N-vinylformamide, 64.8% ofN-vinylpyrrolidone units and 1.4% of N,N'-divinylethyleneurea units(≡30.3 mmol of protonated vinylamine functions) are reacted with 14.7 gof 97% strength sodium chloroacetate (≡122 mmol) and 10 g of 25%strength aqueous sodium hydroxide solution as described in Example 1.11.6 g of carboxymethylated popcorn polymer having 21.6 mol % of unitsof the formula I where R¹, R², R³ are H and Me is Na and 8.1 mol % ofunits of the formula II where R² and R³ are H and Me is Na are obtained.

Example 5

Popcorn polymer 5

25 g of popcorn polymer having the molar composition of 87.7% of 30vinylamine, 4.6% of N-vinylformamide units, 6.6% of N-vinylpyrrolidoneunits and 1.1% of N,N'-divinylethyleneurea units (439 mmol of vinylaminefunctions) are suspended in 770 ml of water in a stirred apparatusequipped with a reflux condenser, two dropping funnels and athermometer. First 26 g (95 mmol) of 99% strength hydrocyanic acid andthen, in the course of 1 hour, 95 g (950 mmol) of a 30% strengthformaldehyde solution are added dropwise at 20° C. The reaction mixtureis stirred for 48 hours at 40° C. After filtration with suction, washingwith water and drying, 55 g of a cyanomethylated product are obtained.This is taken up in 160 g of 10% strength aqueous NaOH and stirred for36 hours at 95° C. while passing through nitrogen and from 800 to 900mbar until no further ammonia escapes from the reaction mixture. Aftercooling to room temperature, the solid is filtered off, washed severaltimes with water and dried for 24 hours at 100° C. and 100 mbar in avacuum drying oven. 80 g of carboxymethylated popcorn polymer having 24mol % of units of the formula I where R¹, R², R³ is H and Me is Na and66 mol % of units of the formula II where R², R³ are H and Me is Na areobtained.

Use Examples

To investigate the complexing power, different amounts of the finelyground popcorn polymers 1 to 4 described above are added to 100 g ofeach of the stock solutions stated below, each of which contains 60 mgof the metal ion stated in the table. The suspension is stirred for 1hour at room temperature, after which the metal ion content of thesolution is determined by complexometric titration with Titriplex IIIsolution. The results are shown in Table 1.

    ______________________________________                                        Stock solutions:                                                              ______________________________________                                        CuSO.sub.4 1.5537       g per l of aqueous solution                             NiSO.sub.4 . 6H.sub.2 O 2.7952 g per l of aqueous solution                    ZnSO.sub.4 . 7H.sub.2 O 2.6694 g per l of aqueous solution                    Hg(NO.sub.3).sub.2 . H.sub.2 O 5.0179 g per l of aqueous solution                                    CaCl.sub.2 . 2H.sub.2 O 2.2114 g per l of                                    aqueous solution                                        MgCl.sub.2 . 6H.sub.2 O 5.0179 g per l of aqueous solution                  ______________________________________                                    

                  TABLE 1                                                         ______________________________________                                        Complexing power of the popcorn polymers 1 to 4                                            Decrease in concentration [%]                                                     Popcorn  Popcorn                                                                              Popcorn                                                                              Popcorn                                  Polymer polymer polymer polymer polymer                                      Metal ion [g] 1 2 3 4                                                       ______________________________________                                        Cu.sup.2+                                                                             0.1      38       33     26     18                                       0.6 100 100 100 57                                                            2.0 100 100 100 100                                                          Ni.sup.2+ 0.1 28 30 17 9                                                       0.6 100 100 84 38                                                             2.0 100 100 100 96                                                           Zn.sup.2+ 0.1 30 33 20 9                                                       0.6 97 97 96 43                                                               2.0 98 98 96 97                                                              Hg.sup.2+ 0.1 85 91 60 34                                                      0.6 93 93 92 92                                                               2.0 94 94 94 93                                                              Ca.sup.2+ 0.1 19 18 14 6                                                       0.6 97 93 61 23                                                               2.0 99 98 98 67                                                              Mg.sup.2+ 0.1 14 13 9 6                                                        0.6 65 60 38 15                                                               2.0 98 98 98 43                                                            ______________________________________                                    

We claim:
 1. An insoluble, only slightly swellable, polymer having modified amino groups, which contains units of the formulae: ##STR7## or both (I) and (II), wherein:R¹ is H or C₁ -C₆ -alkyl; R², R³ are each H, C₁ -C₂₀ -alkyl, aryl or aralkyl; and Me is H or one equivalent of an alkali metal, of an alkaline earth metal or of ammonium.
 2. The insoluble, only slightly swellable, polymer having modified amino groups of claim 1, wherein R¹, R² and R³ are each H.
 3. A process for the preparation of the insoluble, only slightly swellable, polymer having modified amino groups of claim 1, which comprises reacting an insoluble, only slightly swellable, polymer which contains units of the formula (III): ##STR8## wherein R¹ is H or C₁ -C₆ -alkyl, with (1) an α-halocarboxylic acid or an alkali metal, alkaline earth metal or ammonium salt thereof, or(2) an aldehyde and hydrogen cyanide or an alkali metal cyanide, or (3) a cyanohydrin obtained from an aldehyde and alkali metal cyanide; and hydrolysing the adduct formed.
 4. The process of claim 3, wherein from 0.1 to 100% of the units of the formula (III) which are present in the polymer are converted.
 5. The process of claim 3, wherein the reactions are carried out in aqueous suspension.
 6. The process of claim 3, wherein the modification of the units of the formula: ##STR9## where R¹ is H or C₁ -C₆ -alkyl, with the formaldehyde and sodium cyanide is carried out in an aqueous medium.
 7. An ion exchanger based on an insoluble, only slightly swellable, polymer having modified amino groups, which contains units of the formulae: ##STR10## or both (I) and (II), wherein:R¹ is H or C₁ -C₆ -alkyl; R², R³ are each H, C₁ -C₂₀ -alkyl, aryl or aralkyl; and Me is H or one equivalent of an alkali metal, of an alkaline earth metal or of ammonium. 